Printed circuit board

Abstract

A method for producing a circuit board having conductive circuit elements patterened on a non-conductive substrate involves printing a film of a U.V. curable ink composed of a suspension of silver-coated magnetite particles in a U.V. curable resin onto the substrate in a circuit pattern, subjecting the pattern to a magnetic field to move the magnetite particles to a position at or near the upper surface of the resin and effecting U.V. radiation cure of the U.V. curable ink.

What is claimed is: 
     
       1. A method for producing a circuit board having conductive circuit elements with a specific resistivity of less than 0.05 ohm/cm 2  patterned on a non-conductive substrate comprising a. printingn a film of U.V. curable ink onto the non-conductive substrate in a desired circuit pattern, said U.V. curable ink comprising a suspension of silver-coated magnetite particles in a U.V. curable resin.   b. subjecting the resulting printed circuit pattern to a magnetic field sufficient to move the magnetite particles to a position at or near the upper surface of the resin without breaking the surface tension thereof or substantially increasing the thickness of the ink film from said substrate and   c. effecting U.V. radiation cure of the U.V. curable ink by exposing said U.V. curable ink to a U.V. source having an output in the region between 360 nm and 420 nm for a time sufficient to cure said U.V. curable ink.   
     
     
       2. The method of claim 1 wherein said U.V. curable ink comprises a mixture of a cycloaliphatic epoxy resin, and a cationic photoinitiator. 
     
     
       3. The method of claim 2 wherein said U.V. curable resin also contains, as a plasticizer, a plasticizing amount of a polyether polyol. 
     
     
       4. The method of claim 1 wherein said U.V. curable ink contains by volume 25 to 67 percent silver coated magnetite spheres based on the total volume of said curable ink.